上游充通大学 SHANGHAI JIAO TONG UNIVERSITY ixj=kj×i=-k ixk=i k×i=-i k×i=jixk=-j i×i=i×ji=k×k=0 j×i=-k ×i=i × j = k j × i = −k j × k = i k × j = −i k × i = j i × k = − j i × i = j × j = k × k = 0 j j j j